Automotive manufacturers are seeking ways of replacing steel components with aluminum components in order to gain benefits such as reduced weight and improved corrosion resistance. For example, attempts have been made to replace conventional steel autobody sheet with aluminum autobody sheet.
Trimming is an important operation in the autobody sheet forming process. Such trimming operations have conventionally been used to form steel sheet having adequate edge characteristics. When trimmed with dies conventionally designed for steel sheet, aluminum autobody sheet produces unacceptable cut surfaces having slivers, burrs, surface roughness and the like. Slivers are particularly disadvantageous because they cause damage to both the tooling and surface finish of the part. In addition, slivers contaminate the production line.
Aluminum autobody sheet produces appreciable amounts of slivers during trimming operations when trimmed with dies designed for steel sheets. The slivers can be carried to downstream operations and cause damage to the surface of formed parts, resulting in increased repair rates and line downtime. Hand removal of slivers from finished aluminum sheet products is usually employed in production practice. The sliver problem is identified as one of the major factors affecting the OEMs' manufacturing cost gap between using aluminum and steel autobody sheets. As much as a 5 to 10 percent cost reduction for outer panel manufacturing can be achieved if the sliver problem can be resolved.
Another critical concern is trimmed edge burrs which can affect assembly processes and tolerances, scratch other parts in handling, and impose safety hazards in manufacturing and in service of the products. Burrs are also a source of sliver generation in down-stream processes such as hemming
U.S. Pat. No. 5,820,999 to Li et al., which is incorporated herein by reference, discloses an aluminum trimming method which utilizes angled cut conditions. A range of cutting angles is selected such that a wide range of clearances and cutting angles can result in satisfactory cutting operations. The method opens doors for next generation tool design which will not only minimize the current sliver problem and reduce burrs but will also substantially improve the process robustness of trimming aluminum sheets. However, the angled cutting method does not readily apply to existing conventional trimming dies which are configured for zero-degree cutting.
The present invention has been developed in view of the foregoing and to remedy other deficiencies of the prior art.